1. Field of the Invention
The present invention relates to an active matrix liquid crystal display device, and more particularly to a wiring structure of the active matrix liquid crystal display device.
This specification is based on Japanese Patent Application (Application No. Hei 11-189720), the content of which is incorporated herein by reference.
2. Description of the Related Art
FIG. 12 shows an example of the circuitry for a conventional active matrix liquid crystal display device. In the drawing, the active matrix liquid crystal display device includes pixels disposed at respective intersections between data lines K1 to Kn and gate lines G1 to Gm, which are respectively arranged longitudinally and latitudinally, a data driver circuit 200 provided to drive the data lines, and a gate driver circuit 202 provided to drive the gate lines. For each pixel, e.g., pixel 210 formed at the intersection between the gate line Gi and the data line Kj, the pixel is composed of a pixel transistor 212 having a gate connected to the gate line Gi and a source connected to the data line Kj, and liquid crystal capacitance 214 and storage capacitance 216, which are interconnected through the pixel transistor 212.
In the active matrix liquid crystal display device shown in FIG. 12, a polysilicon thin-film transistor is used for the pixel transistor, and the data driver circuit 200 and the gate driver circuit 202 are integrally formed on the same glass substrate as that of the pixel matrix. The data driver circuit 200 is composed of a scanning circuit 222 and an analog switch array 224.
In the foregoing active matrix liquid crystal display device including the driver circuits incorporated therein, a block at a time addressing system is typically used in order to simplify the configuration of the data driver circuit. As shown in FIG. 12, this driving system is a data line driving system adapted to divide data lines into unit blocks, each block being composed of a plurality of lines (4 lines in the shown example); spread video signals in parallel with the data lines of each block; the number of video signal lines being equal to the number of data lines in each block; and then supply the video signals to the data lines through video signal wiring.
In FIG. 12, for example, the blocks are formed such that data lines K1 to K4 constitute a block 1, data lines K5 to KS constitute a block 2, and so on. The data lines K1 to K4 and the data lines K5 to K8 are connected to video signal lines BL1 to BL4, to which video signals are supplied, respectively through the switch transistors Q1 to Q4 and the switch transistors Q5 to Q8 of the analog switch array 224. The same applies to the other blocks. In each block, for all the switch transistors of the analog switch array 224, to which each data line is connected, gates are connected in common, and each gate is connected to one output terminal SPi (i=1 to k) of the scanning circuit 222.
Now, a description will be made of an operation during the block-at-a-time addressing of the active matrix liquid crystal display device constructed in the foregoing manner by referring to a timing chart of FIG. 13. It is assumed that the period for supplying video signals equivalent to one line to be displayed by the liquid crystal display device to data lines K1 to Kn is one horizontal scanning period TH. In one horizontal scanning period TH, the scanning circuit 222 in the data driver circuit 200 sequentially outputs scanning pulses from the output terminals SPi to SPk in synchronization with clock signals DCLK1 and DCLK2 used to control the scanning circuit 222. By these scanning pulses, the switch transistors of the analog switch array 224 are respectively switched ON/OFF by block units.
Then, video signals Vsig equal in number to that of data lines (4 lines in the example of FIG. 12) in one, block are spread in parallel, and input from in-put terminals V1 to V4. Then, the switch transistors of the analog switch array 224 are respectively switched ON/OFF by block units, and thus the video signals are input to the data lines by block units. Such an operation is performed for all the blocks and, in one horizontal scanning period TH, a gate line Gx (x=1 to m) having the gate driver circuit 202 located thereon is driven to a voltage (high level in the example shown in FIG. 12) for switching ON the pixel transistor. As a result, the video signals equivalent to one line are written in the pixels. Further, by performing such an operation sequentially for all the gate lines, two dimensional videos can be displayed on the liquid crystal display device. In FIG. 13, a signal DST denotes a reference signal for defining one horizontal scanning period.
FIG. 14 shows a configuration of a conventional example of an active matrix liquid crystal display device, which includes a precharge circuit 204 provided in a side opposite to the data driver circuit 200, sandwiching a pixel matrix to reset the data lines K1 to Kn before the video signals are written therein in FIG. 12. The precharge circuit 204 is composed of switch transistors N1 to Nn having sources connected to the end portions of the data lines K1 to En and gates connected in common. The drains of the switch transistors N1 to Nn are connected in common, and a precharge signal PCG is input to each gate.
The active matrix liquid crystal display device shown in FIG. 14 is different in operation from the active matrix liquid crystal display device of FIG. 12 in the following respects. The output of the gate driver circuit 202 is made during a horizontal blanking period as a period of outputting no video signals, which is included in one horizontal scanning period. During the horizontal blanking period, the device operates to return the output to a potential for switching OFF all the pixel transistors. While the pixel transistors are in OFF states, precharge signals PCG are applied to the switch transistors N1 to Nn to simultaneously switch ON the switch transistors N1 to Nn constituting the precharge circuit 204. All the data lines K1 to Kn are charged to specified potentials. Other operations are the same as those of the active matrix liquid crystal display device shown in FIG. 12, and thus description thereof will be omitted to prevent repetition.
As described above, block-at-a-time addressing is performed in the conventional active matrix liquid crystal display device. However, in such block-at-a-time addressing, in the block boundary-portion of the adjacent data lines of the liquid crystal matrix, a luminance change occurs because of noise (block noise) generated during switching in the analog switching array of the data driver circuit, which results in the appearance of uneven lines.
To exemplify the above problem, reference is made again to FIG. 12. Through the data lines of the first block, video signals are written in the pixels connected to the respective data lines and, at a next timing, the video signals are written in the respective pixels connected to the data lines, which belong to the second block adjacent to the first block. During the writing of the video signals in the respective pixels connected to the data lines of the second block, the switch transistors Q1 to Q4, constituting the analog switch connected to the data lines of the first block, are in OFF states, and the data lines K1 to K4, belonging to the first block, are in floating states for potentials.
When the switch transistors Q5 to Q8 connected to the data lines of the second block are switched ON and, through the data lines K5 to K8 of the second block, the video signals are written in the pixels connected to the data lines K5 to K8, fluctuation occurs in the potentials of the data lines K5 to K8. Following the potential fluctuation, the data lines K1 to K4 of the first block are also subjected to potential fluctuation because of spatial capacitive coupling with the data lines K5 to K8 of the second block. This situation causes the foregoing problem of block noise.
Another problem inherent in the conventional active matrix liquid crystal display device is the long wiring distance between each driver circuit and the pixel matrix. FIG. 15 schematically shows a structure of the conventional active matrix liquid crystal display device. In the drawing, the active matrix liquid crystal display device is manufactured by attaching a TFT substrate 250 to an opposed substrate 252 by a sealing material, the TFT substrate 250 having a thin-film transistor (TFT) formed as a pixel transistor, and the opposed substrate 252 having common electrode, and then filling liquid crystals in a gap between the two substrates and sealing the gap.
The liquid crystal display device having a driver incorporated therein includes a data driver circuit 200 and gate driver circuits 202 and 206 formed on a glass substrate (TFT substrate); the respective driver circuits, i.e., the data driver circuit 200 and the gate driver circuits 202 and 206 shown in FIG. 15 are generally provided outside a sealing region 254. If the driver circuits are provided inside the sealing region, then voltages supplied to the driver circuits subject liquid crystal molecules to electrolysis, generate impurity ions, and cause deterioration of display images. To prevent this situation, the driver circuits should be provided outside the sealing region.
Another reason for the installation of the data driver circuit 200 and the gate driver circuits 202 and 206 outside the sealing region 254 is as follows. Beads called spacers are scattered between the TFT substrate 250 and the opposed substrate 252 in order to control a gap therebetween, which is filed with the liquid crystals inside the sealing region. If the spacers are placed on the driver circuit, then large pressures are applied only to portions having the spacers when the opposed substrate 252 is laminated on the TFT substrate 250 and attached by applying a pressure. Consequently, short-circuiting occurs between metal layers in the driver circuit, and yield is reduced. To prevent such a situation, the driver circuits should be installed outside the sealing region.
For the foregoing reasons, the wiring distance from the data driver circuit 200 to the pixel, matrix 256, or from the gate driver circuits 202 and 206 to the pixel matrix 256, is limited by the sealing width of the sealing region 254, and becomes longer. Thus, electrostatic coupling capacitance between the data lines is increased and, during block-at-a-time addressing, noise is generated following the voltage fluctuation of the other data lines due to the electrostatic coupling capacitance, resulting in the problem of image quality degradation.
The electrostatic coupling capacitance between the data lines may conceivably be reduced by shielding the data lines from the data driver circuit to the pixel matrix. However, the installation of new metal layers to shield the data lines increases the number of manufacturing steps, and results in a complex device structure.
The present invention was made with the foregoing problems in mind, and it is an object of the present invention to provide an active matrix liquid crystal display device capable of reducing noise generated following voltage fluctuation between data lines and improving image quality without providing any new metal layers for shielding.
FIG. 16 shows a device structure of an active matrix liquid crystal display device for a projector, to which the present invention is applied. The active matrix liquid crystal display device for a projector is irradiated with a strong light to achieve high luminance. The irradiation of a strong light to a pixel thin-film transistor (TFT) results in problems including a reduction in contrast caused by a light leaking current, a generation of vertical crosstalk, and so on. In some cases, accordingly, to prevent the pixel thin-film transistor from being irradiated with a light, upper and lower light shielding metal films 318 and 302 may respectively be provided in the upper and lower portions of the pixel thin-film transistor (a gate is formed by a gate metal film 310, and drain and source regions are formed in a polysilicon layer 306 located below the gate metal film). In the drawing, reference numeral 300 denotes a glass substrate; numeral 304, an insulating film; numeral 308, a gate insulating film; numeral 312, a first interlayer insulating film; numeral 314, a metal film for forming data lines; numeral 316, a second interlayer insulating film; numeral 320, an insulating film; and numeral 322, a transparent electrode film.
According to the present invention, electrostatic coupling capacitance between the data lines is reduced by using metal layers to shield the data lines, which are necessary for structuring the device for purposes other than shielding for wiring, like the lower and upper light shielding metal films 302 and 318.
In order to achieve the foregoing object, an active matrix liquid crystal display device of the present invention comprises: a pixel matrix composed of pixel transistors and pixels that have liquid crystal capacitance and storage capacitance connected to data lines through the pixel transistors, which are disposed at respective intersections between the data lines and gate lines arranged longitudinally and latitudinally, respectively; a data driver circuit for driving the data lines; and gate driver circuits for driving the gate lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside a sealing region located outside the pixel matrix. In this case, all the data lines formed between the data driver circuit and the pixel matrix are covered so as to be surrounded by a metal layer formed for a purpose other than shielding and having a metal different from that of the data lines.
According to the present invention, the active matrix liquid crystal display device comprises: the pixel matrix composed of the pixel transistors and the pixels that have liquid crystal capacitance and storage capacitance connected to the data lines through the pixel transistors, which are disposed at the respective intersections between the data lines and the gate lines arranged longitudinally and latitudinally, respectively; the data driver circuit for driving the data lines; and the gate driver circuits for driving the gate lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside the sealing region located outside the pixel matrix. In this case, all the data lines formed between the data driver circuit and the pixel matrix are covered so as to be surrounded by the metal layer formed for the purpose other than shielding and having a metal different from that of the data lines. Thus, electrostatic coupling capacitance between the data lines can be reduced without providing any new metal layers for shielding. Accordingly, it is possible to reduce noise generated following voltage fluctuation between the data lines, and to improve image quality.
Moreover, since it is not necessary to provide any new metal layers for shielding, it is not necessary to increase the number of manufacturing steps and it is possible to prevent the device structure from becoming complex.
An active matrix liquid crystal display device of the present invention comprises: a pixel matrix composed of pixel transistors and pixels that have liquid crystal capacitance and storage capacitance connected to data lines through the pixel transistors, which are disposed at respective intersections between the data lines and gate lines arranged longitudinally and latitudinally, respectively; a data driver circuit for driving the data lines; and gate driver circuits for driving the gate lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside a sealing region located outside the pixel matrix. In this case, between the data lines formed between the data driver circuit and the pixel matrix, shield wiring by a metal layer having a metal different from that of the data lines and formed for a purpose other than shielding is provided in such a manner that overlapping with the data lines is prevented.
According to the present invention, the active matrix liquid crystal display device comprises: the pixel matrix composed of the pixel transistors and the pixels that have liquid crystal capacitance and storage capacitance connected to the data lines through the pixel transistors, which are disposed at the respective intersections between the data lines and the gate lines arranged longitudinally and latitudinally, respectively; the data driver circuit for driving the data lines; and the gate driver circuits for driving the gate lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside the sealing region located outside the pixel matrix. In this case, between the data lines formed between the data driver circuit and the pixel matrix, the shield wiring by the metal layers having a metal different from that of the data lines and formed for the purpose other than shielding is provided in such a manner that overlapping with the data lines is prevented. Thus, electrostatic coupling capacitance between the data lines can be reduced without providing any new metal layers for shielding. Accordingly, it is possible to reduce noise generated following voltage fluctuation between the data lines, and to improve image quality.
Moreover, since it is not necessary to provide any new metal layers for shielding, it is not necessary to increase the number of manufacturing steps and it is possible to prevent the device structure from becoming complex.
An active matrix liquid crystal display device of the present invention comprises: a pixel matrix composed of pixel transistors and pixels that have liquid crystal capacitance and storage capacitance connected to data lines through the pixel transistors, which are disposed at respective intersections between the data lines and gate lines arranged longitudinally and latitudinally, respectively; a data driver circuit for driving the data lines; and gate driver circuits for driving the gate lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside a sealing region located outside the pixel matrix. In this case, between the data lines formed between the data driver circuit and the pixel matrix, shield wiring by a metal layer having the same metal as that of the data lines is provided in such a manner that overlapping with the data lines is prevented.
According to the present invention, the active matrix liquid crystal display device comprises: the pixel matrix composed of the pixel transistors and the pixels that have liquid crystal capacitance and storage capacitance connected to the data lines through the pixel transistors, which are disposed at the respective intersections between the data lines and the gate lines arranged longitudinally and latitudinally, respectively; the data driver circuit for driving the data lines; and the gate driver circuits for driving the gate lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside the sealing region located outside the pixel matrix. In this case, between the data lines formed between the data driver circuit and the pixel matrix, the shield wiring by the metal layer having the same metal as that of the data lines is provided in such a manner that overlapping with the data lines is prevented. Thus, electrostatic coupling capacitance between the data lines can be reduced without providing any new metal layers for shielding. Accordingly, it is possible to reduce noise generated following voltage fluctuation between the data lines, and to improve image quality.
Moreover, since it is not necessary to provide any new metal layers for shielding, it is not necessary to increase the number of manufacturing steps and it is possible to prevent the device structure from becoming complex.
Furthermore, according to the present invention, a shielding structure of the gate lines formed between the gate driver circuits and the pixel matrix is formed to be the same as that of the data lines.
According to the present invention, since the shielding structure of the gate lines formed between the gate driver circuits and the pixel matrix is formed to be the same as that of the data lines, it is possible to uniformly pressurize the sealing region when the substrate having the pixel transistor formed thereon and an opposed substrate thereof is laminated, and to keep the gap to be filled with liquid crystals uniformly.
Furthermore, according to the present invention, in a side opposite to the data driver circuit of the pixel matrix, pseudo-wiring having the same shielding structure as that of the data lines is provided so as to be extended from the pixel matrix to a peripheral edge side of the substrate.
According to the present invention, since in the side opposite to the data driver circuit of the pixel matrix, the pseudo-wiring having the same shielding structure as that of the data lines is provided so as to be extended from the pixel matrix to the peripheral edge side of the substrate, it is possible to more uniformly pressurize the sealing region when the substrate having the pixel transistor formed thereon and the opposed substrate thereof is laminated, and to keep uniform a gap to be filled with liquid crystals.
An active matrix liquid crystal display device of the present invention comprises: a pixel matrix composed of pixel transistors and pixels that have liquid crystal capacitance and storage capacitance connected to data lines through the pixel transistors, which are disposed at respective intersections between the data lines and gate lines arranged longitudinally and latitudinally, respectively; a data driver circuit for driving the data lines: gate driver circuits for driving the gate lines; and a precharge circuit for precharging the data lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside a sealing region located outside the pixel matrix. In this case, all the data lines formed between the data driver circuit and the pixel matrix, all the data lines formed between the precharge circuit and the pixel matrix, and all pseudo-wiring of a metal layer having the same metal as that of the data lines disposed from the precharge circuit toward a peripheral edge portion of the substrate are covered so as to be respectively surrounded by using a metal layer different from that of the data lines formed for purposes other than shielding.
According to the present invention, the active matrix liquid crystal display device comprises: the pixel matrix composed of the pixel transistors and the pixels that have liquid crystal capacitance and storage capacitance connected to the data lines through the pixel transistors, which are disposed at the respective intersections between the data lines and the gate lines arranged longitudinally and latitudinally, respectively; the data driver circuit for driving the data lines; the gate driver circuits for driving the gate lines; and the precharge circuit for precharging the data lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside the sealing region located outside the pixel matrix. In this case, all the data lines formed between the data driver circuit and the pixel matrix, all the data lines formed between the precharge circuit and the pixel matrix, and all the pseudo-wiring of the metal layer having the same metal as that of the data lines disposed from the precharge circuit toward the peripheral edge portion of the substrate are covered so as to be respectively surrounded by using a metal layer different from that of the data lines formed for purposes other than shielding. Thus, electrostatic coupling capacitance between the data lines can be reduced without providing any new metal layers for shielding. Accordingly, it is possible to reduce noise generated following voltage fluctuation between the data lines, and to improve image quality. Moreover, since it is not necessary to provide any new metal layers for shielding, it is not necessary to increase the number of manufacturing steps and it is possible to prevent the device structure from becoming complex.
An active matrix liquid crystal display device of the present invention comprises: a pixel matrix composed of pixel transistors and pixels that have liquid crystal capacitance and storage capacitance connected to data lines through the pixel transistors, which are disposed at respective intersections between the data lines and gate lines arranged longitudinally and latitudinally, respectively; a data driver circuit for driving the data lines; gate driver circuits for driving the gate lines; and a precharge circuit for precharging the data lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits being formed outside a sealing region located outside the pixel matrix. In this case, respectively between the data lines formed between the data driver circuit and the pixel matrix, between the data lines formed between the precharge circuit and the pixel matrix, and between pseudo-wiring of a metal layers having the same metal as that of the data lines disposed from the precharge circuit toward a peripheral edge portion of the substrate, shield wiring by metal layers having a metal different from that of the data lines and the pseudo-wiring and formed for purposes other than shielding are provided in such a manner that overlapping with the data lines is prevented.
According to the present invention, the active matrix liquid crystal display device comprises: the pixel matrix composed of the pixel transistors and the pixels that have liquid crystal capacitance and storage capacitance connected to the data lines through the pixel transistors, which are disposed at the respective intersections between the data lines and the gate lines arranged longitudinally and latitudinally, respectively; the data driver circuit for driving the data lines; the gate driver circuits for driving the gate lines; and the precharge circuit for precharging the data lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside the sealing region located outside the pixel matrix. In this case, respectively between the data lines formed between the data driver circuit and the pixel matrix, between the data lines formed between the precharge circuit and the pixel matrix, and between the pseudo-wiring of the metal layers having the same metal as that of the data lines disposed from the precharge circuit toward the peripheral edge portion of the substrate, the shield wiring by the metal layers having a metal different from that of the data lines and the pseudo-wiring and formed for purposes other than shielding are provided in such a manner that overlapping with the data lines is prevented. Thus, electrostatic coupling capacitance between the data lines can be reduced without providing any new metal layers for shielding. Accordingly, it is possible to reduce noise generated following voltage fluctuation between the data lines, and to improve image quality
Moreover, since it is not necessary to provide any new metal layers for shielding, it is not necessary to increase the number of manufacturing steps and it is possible to prevent the device structure from becoming complex.
An active matrix liquid crystal display device of the present invention comprises: a pixel matrix composed of pixel transistors and pixels that have liquid crystal capacitance and storage capacitance connected to data lines through the pixel transistors, which are disposed at respective intersections between the data lines and gate lines arranged longitudinally and latitudinally, respectively; a data driver circuit for driving the data lines; gate driver circuits for driving the gate lines; and a precharge circuit for precharging the data lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside a sealing region located outside the pixel matrix. In this case, respectively between the data lines formed between the data driver circuit and the pixel matrix, between the data lines formed between the precharge circuit and the pixel matrix, and between pseudo-wiring of metal layers having the same metal as that of the data lines disposed from the precharge circuit toward a peripheral edge portion of the substrate, shield wiring by metal layers having the same metal as that of the data lines, and formed for purposes other than shielding are provided in such a manner that overlapping with the data lines and the pseudo-wiring is prevented.
According to the present invention, the active matrix liquid crystal display device comprises: the pixel matrix composed of the pixel transistors and the pixels that have liquid crystal capacitance and storage capacitance connected to the data lines through the pixel transistors, which are disposed at the respective intersections between the data lines and the gate lines arranged longitudinally and latitudinally, respectively; the data driver circuit for driving the data lines; the gate driver circuits for driving the gate lines; and the precharge circuit for precharging the data lines. The above elements are all manufactured on the same substrate, and the data driver circuit and the gate driver circuits are formed outside the sealing region located outside the pixel matrix. In this case, respectively between the data lines formed between the data driver circuit and the pixel matrix, between the data lines formed between the precharge circuit and the pixel matrix, and between the pseudo-wiring of the metal layer having the same metal as that of the data lines disposed from the precharge circuit toward the peripheral edge portion of the substrate, the shield wiring by the metal layers having the same metal as that of the data lines and formed for purposes other than shielding are provided in such a manner that overlapping with the data lines and the pseudo-wiring is prevented. Thus, electrostatic coupling capacitance between the data lines can be reduced without providing any new metal layers for shielding. Accordingly, it is possible to reduce noise generated following voltage fluctuation between the data lines, and to improve image quality.
Moreover, since it is not necessary to provide any new metal layers for shielding, it is not necessary to increase the number of manufacturing steps and it is possible to prevent the device structure from becoming complex.
Furthermore according to the present invention, a shielding structure of the gate lines formed between the gate driver circuits and the pixel matrix is formed to be the same as that of the data lines.
According to the present invention, since the shielding structure of the gate lines formed between the gate driver circuits and the pixel matrix is formed to be the same as that of the data lines, it is possible to uniformly pressurize the sealing region when the substrate having the pixel transistor formed thereon and the opposed substrate thereof are laminated. Local pressurizing can prevent the occurrence of short-circuiting between the data lines and the shield wiring.